The northern atmosphere appears ready to hit the reset button and by that I mean the strong blocking pattern we currently have looks set to break down with troughs ready to replace highs. That means a more neutral NAO and the AO within the next 10 days.
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While this may worry some, I believe this is good because the atmosphere is shifting and with a bias negative with both the AO and NAO, it’s the next batch of negative that I believe affects us here in the UK and Western Europe. Why? Because when that AO/NAO returns negative, the atmosphere will be in a more winter time state.
Even with the blocking clearly shown in the below 7-day mean 500mb height anomalies below, you can see the westerly orientation of the trough extending from the N Atlantic in towards the UK underneath, NOT a favourable upper pattern to support any sort of cold here. Often when something isn’t quite right, whether it be a computer or even your car, we often turn things off then back on to correct it. This may be the case with the atmosphere.
Credit: AccuWeather Pro
Day 7-14 sees the collapse of the ridge, replaced by a large trough. That means the Atlantic remains king through the rest of this month as I expected all along.
Credit: AccuWeather Pro
9-16 day
Credit: AccuWeather Pro
In 2009 we saw a negative NAO/AO go positive for a time late in November before a return to negative in early December. We turned cold and snowy between Dec 15-18 as a consequence.
The CFSv2 also sees the breakdown of the major blocking but notice it doesn’t completely loose the positive, hum!
The reason I feel confident about the return of a firm AO accompanied by a negative NAO is the on going activity we’re seeing in the stratosphere above our heads. The warming CONTINUES and there are signs that wave 2 action (early conducive signs of an SSW) is happening now. Often before we get SSW’s or sudden stratospheric warming events, we see the AO/NAO come back up.
Check out the difference between 00 hrs and 240 hrs at 50mb
240 hrs
Here’s the 10mb level
240 hrs
The pressure continues to be put on the vortex.
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Good way of describing it! Hitting “Reset button” in Earth atmosphere… LOL. Super cold for here in Nashville – everyone was running into airport here at 5:30AM CDT as we got off Redeye. Light snow/ice falling, low 20’s, solid ice on rooftops, never reached predicted highs, struggled to,reach brief high somewhere here of 37F officially. By Noon everyone out and about had figured it out and were bundled up as if it was Winter: heavy coats, neck scarves, stocking caps, etc.